Parvamussium vesiculatum Dijkstra, 1995
DIJKSTRA, H. H. 1995. Bathyal Pectinoidea (Bivalvia: Propeamussiidae, Entoliidae, Pectinidae) from New Caledonia and adjacent areas. In Bouchet, P. (Ed.), Résultats des Campagnes MUSORSTOM, Volume 14. Mémoires du Muséum national d'Histoire naturelle, 167: 9-73, figs. 1-154. [p. 37, figs. 59-62, 93-96]
1995 Parvamussium vesiculatum Dijkstra, 1995
H. H. Dijkstra, 1995, figures 55-62, 93-98.
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«TYPE MATERIAL. — Holotype MNHN. Paratypes: 2 AMS C201715, 12 HD, 43 MNHN, 2 NMNZ M268538, 2 NSMT, 2 USNM.
TYPE LOCALITY. — South-east New Caledonia, BIOCAL. stn DW 44, 22°47' S, 167°14' E, 440-450 m.
MATERIAL EXAMINED. — New Caledonia. "Vauban" 1978-79: stn 15, 22°49' S, 167°12' E, 390-395 m, 1 Iv. BIOCAL: stn DW 08, 20°34' S, 166°54' E, 435 m, 1 rv. - Stn DW 44,22°47' S, 167°14' E, 440-450 m, 37 spms, 13 lv, 14 rv (holotype and paratypes). — Stn CP 45, 22°47' S, 167°15' E, 430-465 m, 1 Iv. — Stn DW 46, 22°53' S, 167°17' E, 570-610 m, 1 rv. — Stn DW 49,23°03' S, 16T32' E, 825-830 m, 1 rv. — Stn DW 51, 23°05' S, 16T45' E, 680-700 m, 2 Iv. — Stn DW 106,21°36' S, 166°29' E, 625650 m, 2 spms. MUSORSTOM 4: stn DW 184, 19°04' S, 163°27' E, 260 m, 1 spm. — Stn DW 210, 22°44' S, 167°09' E, 340-345 m, 1 spm, 2 Iv, 1 rv. — Stn DW 222, 22°58' S, 16T33' E, 410-440 m, 2 Iv. — Stn DW 234, 22°15' S, 167°08' E, 350-365 m, 1 spm.
Norfolk Ridge. CHALCAL 2: stn DW 76, 23°41' S, 16T45' E, 470 m, 2 spms. SMIB 3: stn DW 22, 23°03' S, 167°19' E, 503 m, 7 Iv. Loyalty Islands. MUSORSTOM 6: stn DW 479, 21°09' S, 167°55' E, 310 m, 1 Iv. DISTRIBUTION. — New Caledonia and Loyalty Islands, shells in 260-830 m, living in 260650 m.
DESCRIPTION. — Shell small, suborbicular, inequivalve, inequilateral, semi-transparent, up to 6 mm high, left valve slightly more convex than right, auricles unequal in size, umbonal angle ca. 95°.
Prodissoconch ca. 200 μm in height. Left valve widely spaced concentric lirae with strongly developed nodules or hollow scales, broken off in all specimens seen below umbonal region, commencing almost immediately, close-set at first, becoming stronger and more widely spaced towards ventral margin. Irregular radial riblets between concentric lirae. Auricles covered with concentric lamellae, stronger on anterior auricle, slightly closer on posterior auricle. Hinge line straight. Right valve with regularly spaced concentric lirae, very weakly developed near umbonal region. Prodissoconch and dissoconch pellucid. Anterior auricle with 4 delicate radial riblets, which are covered by concentric lamellae that develope into scales on the dorsal margin. Posterior auricle with concentric lamellae, strongly developed on dorsal margin. Byssal fasciole well developed. Internal lirae rudimentary, 5 near anterior and 4 near posterior margin, 1 delicate auricular lira on anterior and a stronger one on posterior of left valve; right valve with 3 rudimentary lirae on anterior, posterior margin with 1 auricular lira on posterior auricle. External sculpture visible from interior of both valves. Resilifer triangular. Byssal notch small, no ctenolium. Both valves semi-transparent white; right valve with a large white spot at centre of disc. Dimensions of the holotype: H 6, L 5.8, D 1.8 mm. REMARKS — A few paratypes lack external sculpture on the left valve (Figs 95-96) after the shell attains 2 mm high, and are very fragile, smooth, glossy and transparent.
Parvamussium vesiculatum most closely resembles P. texturatum which is sympatric and is slightly more orbicular with somewhat larger auricles. The radial costae on the left valve are more prominent in the latter species, whereas concentric lirae are more strongly developed and more widely spaced in P. vesiculatum. P. vesiculatum is ornamented with nodules on the concentric lirae, whereas P. texturatum bears more scales. There are also differences in the internal lirae, which are rudimentary and fewer in number in P. vesiculatum, and well developed in P. texturatum. ETYMOLOGY. — From the nodular sculpture of the left valve (Latin vesiculatus, adj. with nodules).»
HENK H. DIJKSTRA, 1995
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